1. Field of the Invention
The present invention generally relates to rackets for use in games and, more particularly, is concerned with a racket frame having a multi-dimensional cross-sectional construction.
2. Description of the Prior Art
A conventional game racket frame, such as a tennis racket frame, is ordinarily an integral structure which includes a head portion, a throat portion and a handle portion. Typically, the racket frame is fabricated of composite-type material composed of high modulus fibers such as graphite fibers or glass fibers in a matrix of an epoxy resin. Also, racket frames have been fabricated from other materials, such as aluminum, wood and plastics.
The head portion of the racket frame typically has a round or oval configuration and contains a plurality of holes aligned in a common plane for applying stringing under tension and in a grid pattern across the head portion to provide a ball striking area of the racket. The throat portion of the racket frame is a principal structural element of the racket and provides structural connection between the head portion and the handle portion. The handle portion of the racket frame is usually covered with an outer sheath for facilitating gripping of the racket by the user's hand.
The construction of a conventional tennis racket poses several shortcomings to achievement of ball striking accuracy. In one common constructional feature, the cross-section of the racket frame is held constant along the length of the throat and head portion of the racket frame. In another common constructional feature, the cross sectional height of the frame, measured in a direction normal to the plane of the stringing, is varied along the length of the throat and head portion of the racket frame while maintaining the same width of the cross-section, measured in a direction parallel to the stringing, and the same basic geometric cross-section of the racket frame, be it oval, circular, or rectangular shape. These common features can result in either inaccuracies of ball striking directional aim, lower ball striking power or velocity, increased high frequency shock transmitted to the player's arm, reduced effective hitting area of the stringing, reduced maneuverability of the racket frame, or a combination of these deficiencies.
The prior art contains tennis racket constructions which implicitly or explicitly attempt to overcome struck ball directional inaccuracies. Representative of the prior art are the U.S. Patents to Abell (2,164,631), Robinson (2,171,223 and 2,878,020), Brown (2,481,075), Spenle (3,633,910), Tabickman et al (4,192,505), Fernandez (4,436,305), Popplell (4,440,392) and Kuebler (4,664,380 and 4,768,786). The approach of the Kuebler patents is to provide the maximum height (measured in a direction normal to the stringing plane) of the racket frame in a triangular or bight region of the throat portion of the frame where it intersects with the head portion and to taper the height both toward the handle portion and the head portion of the racket frame in opposite directions along the longitudinal axis of the racket.
However, there are practical limitations on how much the frame height can be increased which may restrict the utility of the approach of the Kuebler patents in overcoming one or more of the above-described deficiencies of a conventional racket frame. One limitation is that a significant increase in frame height in the head portion adjacent the throat portion of the frame to stiffen the head portion against deflection may interfere adversely with rebounding of the struck ball off the stringing and thus reduce the effective ball striking area of the racket stringing. Another limitation is that increasing the frame height has the disadvantage of increasing the amount of material in the racket frame and thus frame weight in a corresponding fashion which limits the maneuverability of the frame.
Consequently, in view of the above-described drawbacks of the approach of the prior art patents to overcoming the struck ball directional inaccuracies of conventional tennis racket frame construction, a need still exists for another approach which will overcome these deficiencies without creating new ones in their place.